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I've been meaning for some time (quite a long time actually, since the publication was in May) to post some comments on Kenneth Kuttler's letter to the Journal of 9-11 Studies on estimates for the time to collapse of WTC1. This is not the June 2006 letter in which Kuttler calculates how long WTC7 would have taken to collapse had the initiation been at the top, a matter of no more than academic interest since the final phase of collapse in fact initiated low down in the structure, but his May 2007 letter in which he looks at the Twin Towers, which did in fact collapse from the top down.

Kuttler's letter sets out to estimate the collapse times of the Twin Towers, then to establish lower limits for gravitational collapse times. This is in order to demonstrate that the collapse times observed are inconsistent with gravitational collapse, a commonly repeated assertion from the truth movement. Kuttler is a Professor of Mathematics at Brigham Young and appears to have a respectable record as an academic and teacher. As mathematics is his speciality and the computation involved in this letter is all straightforward arithmetic, I shall assume that all his computed results are correctly derived from his assumptions, and shall focus primarily on the physical feasibility of his assumptions (more the province of a physicist or engineer than of a mathematician) and of the validity of his reasoning from results to conclusions.

In the first paragraph of section 1.1, Kuttler refers to "the claim that the concrete of the floors was essentially all crushed to dust", and refers to the assertion that all the concrete in the Twin Towers was pulverised in his reference 10, an article by Morgan Reynolds. This in turn refers to a single comment by an un-named official taken out of context from an ABC news story which is no longer available but has been archived on a truther website - a less authoritative source would be hard to imagine. This quote of course contains no information about when in the collapse the dust was created, the particle size distribution of the dust or whether larger fragments of concrete were present in other areas of the rubble pile than those in which the un-named official's workers were searching, and disagrees with a wealth of photographic evidence showing macroscopic concrete fragments present in very large quantities in the rubble pile. The date of the reference, September 16th, makes it clear that no significant clearance of debris could have taken place by this time, and that this quote therefore can at most only refer to the absence of large concrete fragments from the upper reaches of the debris pile. In particular, it does not state, or even suggest, that there was no concrete dust in the rubble pile. This will be of significance later in the article.

When Kuttler looks at the actual collapse times, some of the times quoted are not reasonable estimates. Kuttler starts by saying that the collapse time for WTC1 "looks like it came down in about 15 seconds", but then quotes times from the NIST report which are not estimates of the collapse time but of the free-fall time for debris. Legge's estimate, also given as a reference, is an extrapolation without justification from the early moments of the collapse. In discussing his own estimate of the collapse time, Kuttler estimates that the collapse took about 12 seconds after the start of a specific video which he states begins "when the collapse of the top floors has been underway for a few seconds", but he rather misleadingly twice quotes the time "12 seconds" in a discussion which clearly indicates that the collapse time for WTC1 was significantly greater than 12 seconds. His actual estimate of the collapse time is never stated, which seems odd since it is a key part of the analysis.

In section 1.2, Kuttler discusses different collapse modes, specifically what he refers to as "hard top" and "soft top" collapses. The "hard top" model is equivalent to that used by Greening, Bazant and others, and is commonly referred to as "crush-down/crush-up", in which the top part of the building initially destroys the bottom part and then is itself destroyed when it impacts the ground. The "soft top" collapse mode involves simultaneous crush-up and crush-down until the top portion has been destroyed, after which the rubble from the floors destroyed continues to collapse the lower floors. Kuttler argues with considerable justification that the latter model appears more physically reasonable, and then goes on to discuss both models in order to obtain valid comparisons with the work of others. This part of the analysis appears well thought-out and physically reasonable.

In section 1.3 Kuttler sets out the basic physics involved in the collapse, which is generally correctly derived. One quesionable statement from this section is that he has neglected some energy sinks which will therefore increase the collapse time. This will be further discussed in comments on section 1.4.3.

In section 1.4 Kuttler calculates collapse times for the hard top floating floor model. This section is broken down into a series of different sets of starting assumptions, as follows:

Section 1.4.1: Floating floor collapse times considering conservation of momentum only. Kuttler quotes his calculated 12.18 second collapse time as "longer than the official NIST figure of 11 seconds", despite having himself determined the collapse time to be longer than this. Since this letter purports to be a scientific analysis rather than a rebuttal to NIST, it seems inappropriate that he does not compare his results with his own observations. In any case, the figure from NIST is not a collapse time but a free-fall time for loose debris, so Kuttler gives the appearance of deliberately trying to find a shorter time than his calculation for comparison.

Section 1.4.2: Progressive loss of mass to dust. Kuttler assumes 100% loss of concrete in every impact stage of the collapse. This assumes that, in the sequence of floor-to-floor impacts, the entire concrete content of the lower 94 floors has been lost by the time the top impacts the ground. This is a physically unreasonable and completely unjustified assumption. Even if there was no solid concrete remaining in the debris, this does not require that all the concrete involved in a floor-to-floor impact was expelled prior to impact with the ground, as Kuttler assumes; this would require that concrete was not even present as dust in the rubble pile, which the references in the letter do not support. As a result, the collapse times thus calculated will inevitably be unrealistically long. If we simply accept the possibility of dust in the rubble pile, then the requirement for pulverisation to precede the ground impact is removed, as the kinetic energy of the falling debris becomes available in its entirety for pulverisation. If we further accept that macroscopic concrete fragments were present then the energy requirement for pulverisation falls drastically.

Section 1.4.3: Kuttler neglects conservation of momentum and assumes 100% crushing of concrete to 100µm dust. This is physically unreasonable because (a) it has not been established satisfactorily that all the concrete was crushed (see above), and (b) the transfer of energy from kinetic to fracture energy must be limited by conservation of momentum otherwise Newtonian mechanics are violated. Indeed, it is the loss of kinetic energy due to the requirement that momentum is conserved in an inelastic collision that is the source of the fracture energy required for pulverisation, so by neglecting that effect Kuttler is failing to make any attempt at realistic modelling of the physics of pulverisation. The value of 100µm comes from Lioy et al, a paper concerning the sampling of airborne dust at remote sites downwind of the Twin Towers, a sampling technique which would automatically place an upper limit on the dust particle size collected; these samples were therefore in no way representative of the debris from the collapse as a whole, which could have a very much larger particle size distribution. In fact Kuttler himself comments that there was insufficient energy in the collapse to achieve the level of pulverisation he requires, which should alert him to the problems with his own modelling.

Similar comments apply to sections 2.1, 2.2, and 2.3, in which Kuttler calculates collapse times for the soft top model; the quantity and size of dust is not justified, hence the collapse times are unrealistically long. Kuttler does not calculate the collapse time for the soft top model without loss of mass or energy to pulverisation, which is a significant omission.

Section 2.4 seems to be asserting that the steel in the collapse did not contribute to the energy requirements for pulverising concrete but that it should be included as an unrealistic variant of the model to give a shorter collapse time. Quite what Kuttler is trying to say here, I can't really tell.

In section 2.5, analysing the effect of column resistance on the collapse time, Kuttler states that each column exerts an average upwards force during the collapse of between 0.35 and 0.5 of its yield point, making no attempt to justify this figure either by reference or by calculation. This is a serious omission and a key weakness of the paper, as this value is critical to the remaining analysis. His discussion is limited to the following:

"Instead of the acceleration of gravity for g I will use

g = 32 - 2 x 32 x .35.

The 2 in the above is a safety factor which should be somewhere between 2 and 5. A factor of 2 is the smallest reasonable safety factor. The .35 comes about because the column will not deliver its full force over the whole length of the interval. Thus it should be multiplied by some number between .35 and .5."

This last sentence is a bizarre assertion. It is to be assumed that Kuttler is implying that the yield point of each column is at least twice the design loading, which is not entirely unreasonable although not backed up here by reference to any information on the design of WTC1. Since, by definition, at no time can the column exert a greater force than its yield point, this suggests that either the columns were delivering their full strength up to a compression of 35%, or - this is more likely Kuttler's basis for calculation - that their strength declined continuously throughout the collapse in such a way that they were always exerting an upward force whose average value over the collapse was 35-50% of the yield point. This presumes that the support columns were, in effect, slowly bent during the collapse rather than breaking. Since this has no resemblance to the behaviour of steel columns under compressive strain beyond their yield point, his resulting collapse times have no physical meaning whatsoever, and are necessarily a gross overestimate.

In summary, Kuttler in this letter does two things which preclude meaningful analysis.

Firstly, he makes invalid or physically unreasonable assumptions which will lead to greatly increased collapse times. There are four major invalid assumptions amongst those on which the analysis is founded:
(1) There was no concrete in the rubble piles within the footprint of either of the Twin Towers, not even in the form of dust.
(2) The entire concrete content of both towers was pulverised into fragments of 100 microns or less.
(3) Conservation of momentum is not a necessary factor in analysing inelastic collisions.
(4) Collapsing steel columns continue to support significant fractions of their design loads after failure in compressions.
Of these assumptions, (1) is not supported even by the flimsy anecdotal evidence advanced in its support, (2) is based on misinterpretation of airborne dust sampling data, (3) is patently absurd, and (4) is asserted in a highly disguised form and never discussed.

Secondly, either by misinterpretation or veiled implication, he suggests in two places that the collapse time was shorter than his own observations indicate.

While the former could simply be interpreted as an inability to visualise complex situations accurately, the latter - quite blatantly carried out - appears wilfully dishonest. This is the type of propaganda technique of which the truth movement frequently accuses government and media sources, so it is ironic to see it in a scientific communication which purports to seek the truth concerning the 9-11 attacks.

This letter is therefore, in my opinion, primarily a mixture of fatal fallacies and deliberate attempts to mislead. Since its fundamental assumptions are grossly unrealistic, its conclusions are of no value whatsoever.

Dave

__________________"We will punish the murderer together. Our punishment will be more generosity, more tolerance and more democracy."

Hey, that is not just a letter. By nature of its being posted on the website of the Journal for 9/11 Studies, it has become a "peer-reviewed academic paper".

__________________I said lots of things in NPH that I would not say today and that I did not repeat in NPHR, where I specifically corrected at least some of the errors I had made in that earlier book, written 5 years ago.
-David Ray Griffin-

Awkward sentance constructions are those, up with which I shall not put.

He is channeling wise master Yoda.

__________________I said lots of things in NPH that I would not say today and that I did not repeat in NPHR, where I specifically corrected at least some of the errors I had made in that earlier book, written 5 years ago.
-David Ray Griffin-

the transfer of energy from kinetic to fracture energy must be limited by conservation of momentum otherwise Newtonian mechanics are violated. Indeed, it is the loss of kinetic energy due to the requirement that momentum is conserved in an inelastic collision that is the source of the fracture energy required for pulverisation, so by neglecting that effect Kuttler is failing to make any attempt at realistic modelling of the physics of pulverisation.

They all scream that physics must have been violated, and then ignore basic precepts on the behavior of a collision.

Regarding the "factor of safety" of the towers. I think it is entirely reasonble for the towers to have been at a demand to capacity ratio of 1/2 to 1/5.

__________________"Structural Engineering is the art of molding materials we do not wholly understand into shapes we cannot precisely analyze so as to understand forces we cannot really assess in such a way that the community at large has no reason to suspect the extent of our own ignorance." James E Amrhein

Section 1.4.1: Floating floor collapse times considering conservation of momentum only. Kuttler quotes his calculated 12.18 second collapse time as "longer than the official NIST figure of 11 seconds", despite having himself determined the collapse time to be longer than this. Since this letter purports to be a scientific analysis rather than a rebuttal to NIST, it seems inappropriate that he does not compare his results with his own observations. In any case, the figure from NIST is not a collapse time but a free-fall time for loose debris, so Kuttler gives the appearance of deliberately trying to find a shorter time than his calculation for comparison.

This is ridiculous.

Kuttler is simply stating that the times predicted for the WTC twin towers to collapse without any columns holding it up is for all practical purposes the same as the observed "collapse" times.

This means nothing was holding the WTC towers up and proves demoltion. It is the key point of the paper.

Quote:

Similar comments apply to sections 2.1, 2.2, and 2.3, in which Kuttler calculates collapse times for the soft top model; the quantity and size of dust is not justified, hence the collapse times are unrealistically long. Kuttler does not calculate the collapse time for the soft top model without loss of mass or energy to pulverisation, which is a significant omission.

There is no such thing as a "soft top model without loss of mass or energy to pulverisation". "Soft top" means the building-top is pulverized.

Quote:

In section 2.5, analysing the effect of column resistance on the collapse time, Kuttler states that each column exerts an average upwards force during the collapse of between 0.35 and 0.5 of its yield point, making no attempt to justify this figure either by reference or by calculation. This is a serious omission and a key weakness of the paper, as this value is critical to the remaining analysis. His discussion is limited to the following:

"Instead of the acceleration of gravity for g I will use

g = 32 - 2 x 32 x .35.

The 2 in the above is a safety factor which should be somewhere between 2 and 5. A factor of 2 is the smallest reasonable safety factor. The .35 comes about because the column will not deliver its full force over the whole length of the interval. Thus it should be multiplied by some number between .35 and .5."

... or - this is more likely Kuttler's basis for calculation - that their strength declined continuously throughout the collapse in such a way that they were always exerting an upward force whose average value over the collapse was 35-50% of the yield point. This presumes that the support columns were, in effect, slowly bent during the collapse rather than breaking. Since this has no resemblance to the behaviour of steel columns under compressive strain beyond their yield point...

And what are you suggesting here? 0.002 for elastic deformation + 0.03 for the plastic shorting phase? That would be absurd.

Sorry, but even if the columns did buckle and fracture (and I have yet to see any paper prove that they would in the ludicrous free fall collapse scerario supposed by Bazant and endorsed by NIST), the columns then do not just magically disappear.

No, even after conventional failure columns still support a load until fracture. Then the fractured columns pieces support the load during the crushing process and so on.

While Kuttler's value of 0.35 might be unexplained, it certainly is not unreasonable.

Kuttler is simply stating that the times predicted for the WTC twin towers to collapse without any columns holding it up is for all practical purposes the same as the observed "collapse" times.

This means nothing was holding the WTC towers up and proves demoltion. It is the key point of the paper.

Since Kuttler does not state the observed collapse times, he cannot possibly be making any such statement. In fact, his calculated floating floor collapse times are less than the 12 seconds that he states is a few seconds less than the collapse times, so he is very carefully trying to avoid admitting that the predicted floating floor times are significantly less than the observed times. That's dishonest, and it certainly doesn't prove demolition. Why doesn't he state the collapse time?

Originally Posted by bofors

There is no such thing as a "soft top model without loss of mass or energy to pulverisation". "Soft top" means the building-top is pulverized.

Wrong. "Soft top" means that the collapse of the support members propagates both upwards and downwards, and makes no stipulation concerning pulverisation of the non-structural elements of the building. Kuttler makes that quite clear in his definition.

Originally Posted by bofors

And what are you suggesting here? 0.002 for elastic deformation + 0.03 for the plastic shorting phase? That would be absurd.

Suggest some better numbers. I'm happy to look at your derivation of them. Frankly, the single floor buckle scenario strikes me as wildly optimistic anyway, as I've said elsewhere. If you're trying to show that collapse is likely, biasing the results against collapse is valid. If you're trying to prove collapse - which Kuttler isn't - then you have to be rather more passimistic with your assumptions.

Originally Posted by bofors

Sorry, but even if the columns did buckle and fracture (and I have yet to see any paper prove that they would in the ludicrous free fall collapse scerario supposed by Bazant and endorsed by NIST), the columns then do not just magically disappear.

No, even after conventional failure columns still support a load until fracture. Then the fractured columns pieces support the load during the crushing process and so on.

Your absolute faith in the ability of a fractured column to hold up a building, even if the ends of the two halves of the column are not in contact due to lateral dispacement or rotation of the upper section, is not something I share. By simple geometry, the rotation of the falling masses of both WTC towers meant that the upper and lower parts of any severed girders could not have been colinear except for at most those along a single line parallel to the axis of rotation, which at most would have been a minority of the core columns. Yet you seem to think that a structural member can transmit force to another member that it isn't in contact with. That is not a sane belief.

Originally Posted by bofors

While Kuttler's value of 0.35 might be unexplained, it certainly is not unreasonable.

It's a number pulled out of thin air to support a predetermined conclusion, without the slightest shred of justification provided. If he had a justification, why didn't he state it? It's certainly not something which would be expected to be common knowledge. Any conclusions drawn from it are as valid as the original number - which is to say, not at all.

Dave

__________________"We will punish the murderer together. Our punishment will be more generosity, more tolerance and more democracy."

Kuttler is simply stating that the times predicted for the WTC twin towers to collapse without any columns holding it up is for all practical purposes the same as the observed "collapse" times.

This means nothing was holding the WTC towers up and proves demoltion. It is the key point of the paper.

There is no such thing as a "soft top model without loss of mass or energy to pulverisation". "Soft top" means the building-top is pulverized.

And what are you suggesting here? 0.002 for elastic deformation + 0.03 for the plastic shorting phase? That would be absurd.

Sorry, but even if the columns did buckle and fracture (and I have yet to see any paper prove that they would in the ludicrous free fall collapse scerario supposed by Bazant and endorsed by NIST), the columns then do not just magically disappear.

No, even after conventional failure columns still support a load until fracture. Then the fractured columns pieces support the load during the crushing process and so on.

While Kuttler's value of 0.35 might be unexplained, it certainly is not unreasonable.

I'm not sure you are thinking critically about this one Bofors. I suggest making your own models in excel or some spreadsheet. A simple model is not very difficult but really helps to understand the different parameters and their effects on collapse time. For each collision or floor you need to take the following into account:

Energy available = K.E.
Reduction in K.E. due to mass ejection and loss of mass
Energy for comminution of concrete
Energy for elastic compression
Energy for plastic deformation
Momentum transfer

The hard-top is easiest and you can simplify by lumping all energy losses together to get an idea of how much energy can be lost per floor and still have a collapse time close to the observed collapse time. Look at Newtons Bit's analysis of Ross's paper to get an idea about the energies.

You can refine your model by including the soft-top (i.e. the upper floors fail earlier in the collapse. Actually, mass ejection should be some function increasing with time. Energy losses should also increase with time because most are dependent on the strength of the structure which is relatively linear with a ratio from top to bottom of 1:14. You can make it much more complicated but this would be a good start.

Cuttler is wrong about the amount of concrete comminution and Dave's critique regarding the other assumptions is valid. If you try to be as critical about Cuttler's article as you likely are about NIST, I think you will agree it doesn't prove CT.

Kuttler is simply stating that the times predicted for the WTC twin towers to collapse without any columns holding it up is for all practical purposes the same as the observed "collapse" times.

Cooool. Next time I get stopped by a cop for doing 180km/h in a 100km/h area, I can tell him "This is ridiculous, my speed, for all practical purposes the same as the observed speed limit."

__________________It must be fun to lead a life completely unburdened by reality. -- JayUtahI am not able to rightly apprehend the kind of confusion of ideas that could provoke such a question. -- Charles Babbage (1791-1871)My Apollo Page.

And what are you suggesting here? 0.002 for elastic deformation + 0.03 for the plastic shorting phase? That would be absurd.

Sorry, but even if the columns did buckle and fracture (and I have yet to see any paper prove that they would in the ludicrous free fall collapse scerario supposed by Bazant and endorsed by NIST), the columns then do not just magically disappear.

No, even after conventional failure columns still support a load until fracture. Then the fractured columns pieces support the load during the crushing process and so on.

While Kuttler's value of 0.35 might be unexplained, it certainly is not unreasonable.

Actually what is really absurd is the notion that the columns actually had anything to do with the mechanic of the collaspe. It doesn't take a brainac to look at the footage and realise that the structure wasn't falling onto the columns but that it was falling onto the floor trusses and that the columns were being pushed outwards without taking any of the strain of the collapse at all. The whole columns issue is an oily and smelly crimson fish put out by the sham artists that call themselves the "Truth" movement.

__________________It must be fun to lead a life completely unburdened by reality. -- JayUtahI am not able to rightly apprehend the kind of confusion of ideas that could provoke such a question. -- Charles Babbage (1791-1871)My Apollo Page.

I am curious about something. Bofors, and other truthers, talk about free fall and how it had to be a CD. Does a CD really fall at free fall speed like they are insinuating? Has anyone ever timed one and compared to what it should be? Is it even possible to realistically time one?

I'm not sure you are thinking critically about this one Bofors. I suggest making your own models in excel or some spreadsheet. A simple model is not very difficult but really helps to understand the different parameters and their effects on collapse time. For each collision or floor you need to take the following into account:

Energy available = K.E.
Reduction in K.E. due to mass ejection and loss of mass
Energy for comminution of concrete
Energy for elastic compression
Energy for plastic deformation
Momentum transfer

The hard-top is easiest and you can simplify by lumping all energy losses together to get an idea of how much energy can be lost per floor and still have a collapse time close to the observed collapse time. Look at Newtons Bit's analysis of Ross's paper to get an idea about the energies.

You can refine your model by including the soft-top (i.e. the upper floors fail earlier in the collapse. Actually, mass ejection should be some function increasing with time. Energy losses should also increase with time because most are dependent on the strength of the structure which is relatively linear with a ratio from top to bottom of 1:14. You can make it much more complicated but this would be a good start.

Cuttler is wrong about the amount of concrete comminution and Dave's critique regarding the other assumptions is valid. If you try to be as critical about Cuttler's article as you likely are about NIST, I think you will agree it doesn't prove CT.

One of the points I've made about Ross, and what Dave is making here about Kuttler, is that the ADDITIONAL "Energy for comminution of concrete" is ZERO MJ.

__________________"Structural Engineering is the art of molding materials we do not wholly understand into shapes we cannot precisely analyze so as to understand forces we cannot really assess in such a way that the community at large has no reason to suspect the extent of our own ignorance." James E Amrhein

A CD was timed by E. Yarimer and C. Brown for two highrise buildings in the UK in 1995. The results were published in the Conference Proceedings: "Structures Under Shock and Impact IV, 1996". The collapse rates were considerably slower than freefall and showed an intriguing delay of about 1.8 seconds after the explosive charges were detonated.

A CD was timed by E. Yarimer and C. Brown for two highrise buildings in the UK in 1995. The results were published in the Conference Proceedings: "Structures Under Shock and Impact IV, 1996". The collapse rates were considerably slower than freefall and showed an intriguing delay of about 1.8 seconds after the explosive charges were detonated.

So as far as CDs are concerned, all that truther talk of "free-fall" collapses means, well....nothing.

That's only if you use an inelastic collision. You can use an elastic collision and then subtract the energy for plastic work. Same thing really. Or am I missing something?

If it's an elastic collision, there is no plastic work. You can use something inbetween with a coefficient of restitution that isn't 100%, but then there's even less damage to the colliding objects.

__________________"Structural Engineering is the art of molding materials we do not wholly understand into shapes we cannot precisely analyze so as to understand forces we cannot really assess in such a way that the community at large has no reason to suspect the extent of our own ignorance." James E Amrhein

So as far as CDs are concerned, all that truther talk of "free-fall" collapses means, well....nothing.

No, you don't get it. see the explosives blew the air out of the building leaving a vaccum, this sucks the building down causing it to fall faster then freefall....

Seriously I had a Truther try and convince me of this.

__________________It must be fun to lead a life completely unburdened by reality. -- JayUtahI am not able to rightly apprehend the kind of confusion of ideas that could provoke such a question. -- Charles Babbage (1791-1871)My Apollo Page.

A CD was timed by E. Yarimer and C. Brown for two highrise buildings in the UK in 1995. The results were published in the Conference Proceedings: "Structures Under Shock and Impact IV, 1996". The collapse rates were considerably slower than freefall and showed an intriguing delay of about 1.8 seconds after the explosive charges were detonated.

What is so intriguing about the delay? That's the way the charges were set.

A CD was timed by E. Yarimer and C. Brown for two highrise buildings in the UK in 1995. The results were published in the Conference Proceedings: "Structures Under Shock and Impact IV, 1996". The collapse rates were considerably slower than freefall and showed an intriguing delay of about 1.8 seconds after the explosive charges were detonated.

Thank you Apollo. I was curious, because this would apparently refute bofors claim of CD because of the fall rate.

Thank you Apollo. I was curious, because this would apparently refute bofors claim of CD because of the fall rate.

Well, I am not sure of that, since it seems that most CTs propose that the WTC towers were blown apart floor by floor, top down, which is not characteristic of a normal CD, which blows out a few floors, then lets gravity do the rest, just like the 'crush down' phase of Bazant and Verdure.

Although I can't think of a comparison for the sort of CD that Truthers propose for WTC 1 and 2, since it has never happened before to my knowledge

A CD was timed by E. Yarimer and C. Brown for two highrise buildings in the UK in 1995. The results were published in the Conference Proceedings: "Structures Under Shock and Impact IV, 1996". The collapse rates were considerably slower than freefall and showed an intriguing delay of about 1.8 seconds after the explosive charges were detonated.

That's extremely interesting. Quite apart from indicating that the free-fall claims are completely irrelevant, it suggests that Griffin's claim that CD is characterised by a rapid onset is also specious.

Dave

__________________"We will punish the murderer together. Our punishment will be more generosity, more tolerance and more democracy."

So as far as CDs are concerned, all that truther talk of "free-fall" collapses means, well....nothing.

Originally Posted by PhantomWolf

Quote:

No, you don't get it. see the explosives blew the air out of the building leaving a vaccum, this sucks the building down causing it to fall faster then freefall

....

Quote:

Seriously I had a Truther try and convince me of this.

Originally Posted by cmcaulif

Well, I am not sure of that, since it seems that most CTs propose that the WTC towers were blown apart floor by floor, top down, which is not characteristic of a normal CD, which blows out a few floors, then lets gravity do the rest, just like the 'crush down' phase of Bazant and Verdure.

Although I can't think of a comparison for the sort of CD that Truthers propose for WTC 1 and 2, since it has never happened before to my knowledge

Yes usually it is claimed that the explosives were timed to take each floor out sequentially so that it would fall quickly but not be noticeable. why ? I think it was planned that way by the NWO to give fodder to CT's. It must have been hard to time the thermite burning through the steel precisely at the right time. OF course the vacuum effect of blowing all the air of the building also helped in pulling down the building. I have also heard a claim it went so fast because the government was testing a secret gravity enhancing device. I kid you not.

A CD was timed by E. Yarimer and C. Brown for two highrise buildings in the UK in 1995. The results were published in the Conference Proceedings: "Structures Under Shock and Impact IV, 1996". The collapse rates were considerably slower than freefall and showed an intriguing delay of about 1.8 seconds after the explosive charges were detonated.

Just to add to the time frame discussion...

According to a Controlled Demolition, Specialist, the Daughter Louizex- stated in the documentary, Wrecking Ball, on the discovering channel, a 14 story hospital brought down in 7 seconds.

__________________"I would imagine that if you took the top expert in that type of work and gave him the assignment of bringing these buildings down with explosives, I would bet that he could do it."-John SKilling-Head Structural Engineer WTC-1993 Seattle Times

these did all start at around the bottom. These smear-o-grams are in fact y=y(t) diagrams, obtained by the extraction of 1xN bitmaps at a fixed position of the videos and merged to a singe bitmap. I can't see the difference.

Fools and idiots fall for the those falling time idiot papers? 9/11 truth can not do simple physics to calculate what happen on 9/11 by gravity. More lies from 9/11 truth.

What does it take to suspend rational thought?

9/11 truth trash talk is old now, only a few people who are too lazy to learn the tools needed to show 9/11 truth is full of lies. It has been 6 years, the open minds must be clear of dust by now, try some education.

Stupid silly ideas and unable to figure out the WTC towers fell due to fire and gravity. Why? What makes an engineer so biased they are unable to do simple physics? Why is 9/11 truth wrong on everything?

The biggest group of liars who are unable to collect any evidence or facts to back up their conclusions. Is this paper another in this collection of lousy work by biased people with doltish ideas of woo on 9/11?

these did all start at around the bottom. These smear-o-grams are in fact y=y(t) diagrams, obtained by the extraction of 1xN bitmaps at a fixed position of the videos and merged to a singe bitmap. I can't see the difference.

einsteen, very interesting. Although something that should be noted from what Appollo mentioned earlier, is that the explosions in a CD occur before the collapse begins. So we should expect to hear and see the explosions, as well as blown out windows from over pressure, all before collapse initiation.

Indeed CM, for wtc7 you would expect some booms first before the collapse. The building at the right top was wtc7. If you make such a diagram for wtc1,2 you would see it also looks the same although it started at a high floor. This is of course because it starts with a huge mass in motion and that will always start slowly.

The 2 in the above is a safety factor which should be somewhere between 2 and 5. A factor of 2 is the smallest reasonable safety factor. The .35 comes about because the column will not deliver its full force over the whole length of the interval. Thus it should be multiplied by some number between .35 and .5."

Holy Moses, smell the roses! This guy is just pulling stuff out of thin air. I don't see how he can make the formula above work in any reasonable way. Make the factor of safety 0.8 which means the building is falling under its own load and he STILL gets a reduction in accelleration.

The problem is he can't just make up an equation like he did here. It has to have been derived in some way instead of this frankenstein creation.

By the way, impact loading STARTS at 2x static load so his factor of safety is gone right there.

Finally, the 0.35 to 0.5 factor is meaningless. "Not deliver it's full force over the whole length"? Did he calculate the wave speed in steel? Most assuredly not. Again, you can't pull numbers and fudge factors out of your arse that have no basis in formula or observation. This is not engineering and looks like a hoax to me.

Indeed CM, for wtc7 you would expect some booms first before the collapse. The building at the right top was wtc7. If you make such a diagram for wtc1,2 you would see it also looks the same although it started at a high floor. This is of course because it starts with a huge mass in motion and that will always start slowly.

Just out of interest, what are the other four?

Dave

__________________"We will punish the murderer together. Our punishment will be more generosity, more tolerance and more democracy."

If it's an elastic collision, there is no plastic work. You can use something inbetween with a coefficient of restitution that isn't 100%, but then there's even less damage to the colliding objects.

That's essentially what I mean. You can model the "in between" collisions iteratively using conservation of momentum and long as you remove the energy at each iteration that goes into destroying stuff and/or is dissipated as heat. This makes the energy more tangible.

The 2 in the above is a safety factor which should be somewhere between 2 and 5. A factor of 2 is the smallest reasonable safety factor. The .35 comes about because the column will not deliver its full force over the whole length of the interval. Thus it should be multiplied by some number between .35 and .5."

I'm sorry, I am still hung up on this equation the guy put out there. He says the factor of safety goes from 2 to 5. Ok, let's use 5.

g = 32 - 5 x 32 x 0.35 = -24 ft/sec^2

Wow! Now the tower is accellerating UP. It is growing taller! Amazing. Test your boundary conditions to see if they make sense. If they don't, your made up equation probably does not reflect reality.

I'm sorry, I am still hung up on this equation the guy put out there. He says the factor of safety goes from 2 to 5. Ok, let's use 5.

g = 32 - 5 x 32 x 0.35 = -24 ft/sec^2

Wow! Now the tower is accellerating UP. It is growing taller! Amazing. Test your boundary conditions to see if they make sense. If they don't, your made up equation probably does not reflect reality.

To be fair on Kuttler, it's reasonable to suppose he means this to be the maximum force the column can exert, so the acceleration can be taken never to be negative. Even so, his boundary conditions do indeed make nonsense of his numbers. If we take his minimum value for the fraction of force exerted, 0.35, this gives the result that a steel structure with a safety factor of three is indestructible. His maximum value implies that no steel structure ever built can possibly collapse. Of course, this says nothing about the method of collapse initiation, so the inference to be drawn is that even controlled demolition using explosives is at best marginal and, for most cases, impossible. Kuttler has therefore effectively disproved that WTC7 was a CD by disproving the very feasibility of CD.

Dave

__________________"We will punish the murderer together. Our punishment will be more generosity, more tolerance and more democracy."

I never went through that paper because it is a jumble (combining computer notations with proper math notations), but I think the maximum (dynamic) strength can be determined in the following way. If we know the static force and compare that with the Energy loss per story divided by h, which is in fact the average force (used by Bazant) the peak force should be high in order to get the same area, see this image

I never went through that paper because it is a jumble (combining computer notations with proper math notations), but I think the maximum (dynamic) strength can be determined in the following way. If we know the static force and compare that with the Energy loss per story divided by h, which is in fact the average force (used by Bazant) the peak force should be high in order to get the same area, see this image

That's exactly how I understand it. The problem is, by definition Fmax is the yield point, which is therefore the product of the design load and the safety factor, so Kuttler is looking for the average to be between one third and one half the maximum. This implies a force vs distance curve varying as a function between 1-x and 1-x^2 over the entire height of the collapse to the next impact (1-x gives a value of 0.5, 1-x^2 gives 1/3 which I assume is where Kuttler gets his numbers - I didn't want to put this in the OP because I'm just second-guessing Kuttler). That's assuming far too much resilience from a steel column, and as I pointed out above it would mean that most steel structures were indestructible.

Originally Posted by einsteen

Dave,

The one left down is the Landmark implosion, I forgot the other ones and have to go through my video archive at home.

What acceleration do you get from Landmark? From the height and collapse time it looks to me like it dropped at about 0.4g, which is way, way below freefall. However, as far as I can tell, Landmark was hybrid concrete and steel construction, and based on a total absence of structural engineering experience I'd expect concrete to fail very differently in compression from steel.

Dave

__________________"We will punish the murderer together. Our punishment will be more generosity, more tolerance and more democracy."

That's essentially what I mean. You can model the "in between" collisions iteratively using conservation of momentum and long as you remove the energy at each iteration that goes into destroying stuff and/or is dissipated as heat. This makes the energy more tangible.

You're mixing mechanical energy and potential (or kinetic) energy. It's difficult to do correctly. The kinetic energy loss of an inelastic collision is the energy that goes into strain energy (in this case the slab, i.e. pulverized concrete), heat energy and sound energy. There's enough energy there from the very first collision to turn about 5% of one slab into fine dust, with a little change left over for heat and sound.

__________________"Structural Engineering is the art of molding materials we do not wholly understand into shapes we cannot precisely analyze so as to understand forces we cannot really assess in such a way that the community at large has no reason to suspect the extent of our own ignorance." James E Amrhein